Self-loading scraper hydraulic circuit with diverter



June 4, 1968 J. A. JUNCK ET AL 3,386,344

SELF-LOADING SCRAPER HYDRAULIC CIRCUIT WITH DIVERTER Filed Sept. 30, 1966 3 Sheets-Sheet I INVENTORS JOHN A. JuNcK JosEPH KOKALY P .1 E l BY n JAMEs E. SCHEIDT ATTORNEYS June 4, 19 68 u cK ET AL v 3,386,344

SELF-LOADING SCRAPER HYDRAULIC CIRCUIT WITH DIVERTER Filed Sept. 30, 1966 3 Sheets-Sheet z INVENTORS E J. E JOHN A. JUNCK JOSEPH KOKALY 1 JAMES E. SCHEIDT June 4, 1968 J, u cK ET AL 3,386,344

SELF-LOADING SCRAPER HYDRAULIC CIRCUIT WITH DIVERTER Filed Sept. 30, 1966 5 Sheets-Sheet 5 J mv zgmoxs OHN- UNCK E r 3 JOSEPH KOKALY JAMES E. SCHEIDT United States Patent 3,386,344 SELF-LOADING SCRAPER HYDRAULIC CIRCUIT WITH DIVERTER John A. .lnnck, Joseph Kokaly, and James E. Scheidt, Joliet, 11]., assignors to Caterpillar Tractor Co., Peoria, 11]., a corporation of California Filed Sept. 30, 1966, Ser. No. 583,243 Claims. (Cl. 91-414) ABSTRACT OF THE DISCLOSURE A hydraulic circuit especially useful in self-loading scrapers wherein multiple elevator mechanism speeds are provided. The highest speed ranges of the elevator mechanism are achieved by diverting a portion of the hydraulic fluid used for steering the vehicle to feed the elevator motor. Another portion of the steering hydraulic fluid is available to the steering valves at all times. Upon demand, the portion of the steering hydraulic fluid used for driving the elevator mechanism at the higher speeds is rediverted back to the steering valve.

The present invention relates to hydraulic control circuits and more particularly to a hydraulic control circuit for a self-loading scraper.

Self-loading scrapers utilizing elevator mechanisms to assist in loading the scraper bowl have recently been developed as high production earth moving tools which are expected to work with and in competition with push loaded scrapers of the more conventional and long utilized design. This high production work requires that a number of elevator drive speeds be provided for etlicient loading of various types of materials. It is further advantageous to provide a number of elevator drive speeds in order that the flight velocity of the individual elevator components can be matched to the forward speed of the vehicle and the velocity at which the material is flowing over the scraper cutting edge.

To achieve the above noted desirable features, multiple or infinite speed elevator drive mechanisms have been provided in the past. However, many of these require special electric drive arrangements or expensive variable displacement hydraulic pumps at costs which are prohibitive or which are adaptable only to vehicles having electrical traction systems. I

Other prior art multiple speed elevator drive mechanisms provide for combining hydraulic fluid which supplies the scraper bowl and ejector controls with the elevator drive pump fluid for providing higher speed drive, whereas use of the elevator drive pump fluid alone provides an elevator slow speed drive. Such arrangements, however, are often unsatisfactory since priority must of necessity be given to the bowl and ejector control circuits. This occurs because adjusting the depth of cut during any load cycle is accomplished by raising or lowering the bowl whereby the speed of the elevator is frequently reduced. The result is poor loading efliciency due to the erratic speed of the elevator as compared to the relatively constant forward movement of the vehicle and velocity of material flowing over the cutting edge.

The present invention provides a hydraulic circuit for driving self-loading scraper elevator mechanisms wherein multiple elevator speeds may be obtained at the desire of the operator but wherein these multiple elevator speeds are obtained without interfering with other vital and desirable functions of the vehicle. Further, such versatility is obtained in a relatively simple and economical m'anner.

By virtue of the present invention and the novel arrangement of the components thereof a portion of the hydraulic fluid used for steering the scraper is diverted to feed the elevator motor to produce higher speed ranges thereof. Since at least a portion of the steering hydraulic fluid is available to the steering valves at all times, the scrape-r will remain under directional control even while the elevator mechanism is operating at higher speeds. The diversion of a portion of the steering hydraulic fluid to operate the elevator mechanism is particularly advantageous during loading of the scraper bowl, since the vehicle is normally travelling in a straight line. Even when the direction of the vehicle is corrected, slow steering speeds are ordinarily quite suitable whereby only a portion of the total available steering hydraulic fluid is necessary for the steering function.

Accordingly, it is an object of the present invention to provide a hydraulic control circuit for a self-loading scraper to drive an elevator capable of running at multiple speed ranges.

It is another object of the invention to provide hydrau lical-ly driven power means for a self-loading scraper elevator wherein higher speeds of the elevator mechanism are obtained by diverting hydraulic fluid from the steering circuit into the elevator drive circuit.

Another object off the present invention is to provide a self-loading scraper elevator control circuit wherein the elevator is driven at multiple speeds without affecting the scraper ejector and bowl control circuit operation.

Still another object of the invention is to provide a self-loading scraper elevator control circuit that utilizes hydraulic fluid diverted from the scraper steering control circuit to attain higher elevator speed ranges, but wherein steering control is still effectively maintained.

Further and more specific objects and advantages of the invention are made apparent in the following specification wherein several forms of the invention are described by reference to the accompanying drawing.

In the drawing:

FIG. 1 is a schematic illustration showing one embodiment of the elevator control system of the present invention in conjunction with bowl control means, ejection means and elevator motor and steering control means;

FIG. 2 is a schematic illustration showing another embodiment of the control system of the present invention wherein a greater number of elevator speed ranges are produced than for the circuit illustrated in FIG 1; and

FIG. 3 is a schematic illustration showing the control system of the present invention where hydraulic fluid is directed from the steering circuit to the elevator control circuit and vice versa through an automatic diverter control means.

Referring now to 'FIG. 1, a valve group 1 1 comprising a bowl valve 12, an ejector valve 13 and elevator control valve .14 control the bowl jacks 16, ejector jack 17 and elevator motor 18 respectively. Additionally a steering valve 19 controls the scraper steering mechanism (not shown). A first fluid pump 21 draws hydraulic fluid from reservoir 22 and delivers it via conduit 23 to the inlet side of bowl control valve 12. This hydraulic fluid is further delivered to ejector control valve 16 from bowl control valve .12 via interconnecting conduit 24.

in the event both bowl control valve 12 and ejector control valve .13 are in their neutral position, hydraulic fluid entering through conduits 23 and 24 respectively is exhausted through passageways 25 and 26 in the valve body 27 of elevator control valve 14. From thence the hydraulic fluid passes through return conduits 28 and 23 back into reservoir 22.

Bowl control valve 12 positions bowl jacks 16 by passing hydraulic fluid either through conduit 31 or through conduit 32 while these same conduits act alternatively as return conduits for hydraulic fluid forced out of the bowl jacks 16. Exhaust fluid returning either through conduit 31 or conduit 32 passes back through bowl control valve 12 and from thence through interconnecting conduits 33 and 34 through ejector control valve 13 and into passageways 3'6 and 37 in elevator valve body 27. From thence the exhaust fluid passes into return conduits 28 and 29 into reservoir 22.

Ejector jack 1-7 communicates with ejector control valve 113 through conduits 38 and 39 (and 32) respectively. As in the case of the bowl control circuit, hydraulic fluid exhausted from the ejector circuit passes out either through passageways 36 or 37 into return conduits 28 and 2-9 and from thence to reservoir 22.

Further details of the operation of the bowl control circuit and ejector control circuit are not set forth to any extent herein, as these circuits do not comprise any portion of the present invention, but are merely presented to illustrate how such circuits cooperate with the elevator control and steering control circuits which are the subject of the present invention. Complete details as to the operation of similar bowl and ejector control circuits may be obtained by reference to Patent No. 3,258,926 issued July 5, 1966 for Hydraulic Control Circuit for Self-Loading Scrapers.

A second pump 41 draws hydraulic fluid from reservoir 22. The output of pump 41 communicates via conduit 42 with elevator motor 18 as well as with inlet port 43 of elevator control valve 14 through a branching conduit 44.

Exhaust fluid from elevator motor 18 empties through conduit 46 and connecting return conduit 29 into reservoir 22. Inlet port 43 opens into annulus 47 for-med into a bore 48 in elevator valve body 27.

Elevator control valve spool 49 is translationally retained within bore 48. A land 51 on valve spool 49 permanently blocks communication between annulus 47 and passageway 25. A second land 52, axially displaced from land 51 on control valve spool 49, serves to either block or permit communication between annulus 47 and passageway 36 depending upon the translational position of control valve spool 49 in bore 48.

Hydraulic fluid to actuate the steering circuit of the self-loading scraper is supplied by third and fourth pumps 53 and 54, respectively, drawing fluid from reservoir 22. The fluid output of third pump 53 is communicated to the inlet side of steering valve 19 directly through conduit 56.

The fluid output of fourth pump 54 is communicated to the inlet side of steering valve 19 through another conduit 57. In addition, however, a manually actuated diverter valve 58 is interposed in conduit 57 at any point between the output of fourth pump 54 and the inlet of steering valve 19.

Diverter valve 58' comprises a valve body 59 having a transverse bore 61 therein. Diverter valve spool 62 is in turn disposed within bore 61. A land 63 formed on one end of spool '62 bears against a return spring 64 which in turn bears against a recess in one end of valve body 59. The other end of spool 62 extends outwardly from valve body 59 and terminates in a connection (indicated by the dashed line) extending to the foot operated control lever 66.

"Control lever 66 is mounted such that pressure of the opera-tors foot thereon moves valve spool 62 to the left against the force of return spring 64. On the other hand, removal of foot pressure from control lever 66 permits return spring 164 to force valve spool 62 into the extreme right-hand position as illustrated in FIG. 1.

When spool 62 is in the extreme right-hand position as shown, hydraulic fluid from fourth pump 54 is communicated from inlet passageway 67 across groove 68 on spool 62 to outlet passageway 69. Outlet passageway 69 in turn communicates with conduit 57 and from thence to the inlet of steering valve .19.

Inlet passageway 67 also communicates through check valve 71 to bore 61. However, as illustrated in FIG. 1,

when spool 62 is in the extreme right-hand position, further communication is blocked by land 72. However, when spool 62 is forced into the left-hand position under foot pressure exerted by control lever 66, communication is unblocked to permit fluid to flow into second outlet passageway 73. At the same time land 72 interrupts flow between inlet passageway 67 and first outlet passageway 69'.

Second outlet passageway 73 in turn communicates with conduit 74 which at its other end merges int-o conduit 42 on the downstream side of second pump 41. Operation of the aforedescribed system to produce multiple speed ranges in the scraper elevator is as follows:

First it should be noted that at all times third pump' 53 supplies hydraulic fluid uninterruptedly to steering valve 19 to effectuate slow speed steering of the self-loading scraper vehicle. As illustrated in FIG. 1, the elevator circuit is in neutral whereby the elevator mechanism is not in operation.

As the elevator mechanism is not in operation, there is no need for hydraulic fluid being directed to elevator motor .18, and subsequently the foot control lever 66 is inactivated whereby diverter spool 62 is in the extreme right-hand position. In such position the output of fourth pump 54 is communicated directly across diverter valve 58 into conduit 57 whereby the output of fourth pump 54 is combined with the output of third pump 53 to supply a sufficient volume of hydraulic fluid to steering valve .1 9 to drive the vehicle steering motors (not shown) at high speed.

At the same time, output of second pump 41 is directed through conduit 42, branching conduit 44, through annulus 47 and bore 48 into return passageway 26. From thence it returns via return conduits 28 and 29 into reservoir 22. As there is free flow of hydraulic fluid directly from second pump 41 into reservoir 22, hydraulic fluid cannot be forced through elevator motor 18 whereby the elevator mechanism remains idle.

When the vehicle operator desires to drive the elevator mechanism at slow speed, as for instance when loading material from the borrow pit, he manually moves control valve spool 49 to the extreme rightward position in bore 48. In this position land 52 blocks communication between annulus 47 and return passageway 26 whereby output fluid from second pump 41 passes through conduit 42 and is forced through elevator motor 18. Thus actuated, elevator motor 18 drives the elevator mechanism through conventional mechanical linkages (not shown). Hydraulic fluid is exhausted from elevator motor 18 through connecting conduit 46 and return conduit 29 into reservoir 22.

If it becomes necessary, or should the vehicle operator desire to drive the elevator mechanism at a high speed, he applies foot pressure to control lever 66 whereby diverter spool 62 is forced to the extreme leftward position thereby blocking communication between fourth pump 54 and the inlet of steering valve 19, but at the same time opening communication between inlet passageway 67, check valve 71 and second outlet passageway 73.

The output of fourth pump 54 is thereby communicated into conduit 74 and the hydraulic fluid from thence combines with the fluid output of second pump 41 in conduit 42. The augmented fluid flow passes through conduit 42 into elevator motor 18 driving it at a higher speed than previously noted.

Should the vehicle operator no longer desire to drive the elevator mechanism at high speed, or should he desire to maneuver the scraper vehicle more quickly, he removes his foot from control lever 66 whereby return spring 64 forces spool 62 to the extreme rightward position, thus restoring communication between fourth pump 54 and the inlet of steering valve 19. At the same time communication between fourth pump 54 and conduit 74 is interrupted and the fluid volume flow in conduit 42 returns to that supplied solely by second pump 41.

To completely stop elevator operation the vehicle operator need only return control valve spool 49 to the neutral position whereby the output of second pump 41 flows directly back to reservoir 22 via the route as previously described. Thus it is seen that by actuation of the control valve 14 and the additional actuation of control lever 66 the vehicle operator may select to operate the elevator mechanism in either a slow or high speed range or not at all.

Utilizing the identical principles of the circuit as illustrated in FIG. 1, but altering somewhat the elevator control valve construction and adding a fifth pump to the control circuits, additional selectable speed ranges of the elevator mechanism of a self-loading scraper are achieved. Such an elevator control circuit, capable of driving an elevator mechanism in four different speed ranges is illustrated in FIG. 2 of the drawing.

With respect to the bowl and ejector control circuits, this multiple speed circuit of FIG. 2 is identical with that described in FIG. 1. Therefore any description of that portion of the scraper control circuit will not be repeated. Further, for purposes of easy comparison, equivalent parts in FIG. 2 are identified with the same numerals as those in FIG. 1 with the exception that a prime is added.

As illustrated in FIG. 2, second pump 41 draws hydraulic fluid from reservoir 22 to force such fluid into conduit 42'. In the identical manner as the control circuit of FIG. 1, the hydraulic fluid in conduit 42 is communicated through annulus 47', bore 48' into return passageway 26, from thence into return conduit 29 to reservoir 22'.

In addition hydraulic fluid in conduit 42 communicates with elevator motor 18' via connecting conduits 81 and 82. Elevator motor 18 is in turn communicated with reservoir 22 through return conduit 83.

The steering circuit of the control system illustrated in FIG. 2 is identical with that previously described in respect to FIG. 1. That is, hydraulic fluid to actuate the steering circuit of the self-loading scraper is supplied by third and fourth pumps 53 and 54' respectively. The output of third pump 53' is supplied to the steering valve 19 directly and independent of the output of fourth pump 54.

Diverter valve 58' and its foot actuated control lever 66' are identical in construction with the diverter valve and foot control lever illustrated in FIG. 1. Further, as in the case of the control circuit of FIG. 1, diverter valve 58 either permits hydraulic fluid to flow from the output of pump 54 directly to steering valve 19 or alternately directly from the output of pump 54' into conduit 74 from whence the pressure fluid is combined with the output of pump 41 in conduit 42. The alternate paths of fluid flow, as in the case of the control circuit of FIG. 1, is controlled by the actuation of control lever 66'.

Unlike the control circuit of FIG. 1, a fifth pump 84 is included in the circuits of FIG. 2. Fifth pump 84 draws hydraulic fluid from reservoir 22' through conduit 86. The output of pump 84 is conducted into conduit 87 from whence on the one hand it passes through a check valve 88 to connect into conduit 82 leading into elevator motor 18'.

On the other hand, branch conduit 89 connects conduit 87 just upstream of check valve 88 with an inlet 90 in elevator control valve body 27. Inlet 90 communicates with an annulus 91 formed into bore 48'. In turn bore 48 opens into passageway 37 that communicates directly with return conduit 29'. A land 92 permanently blocks communication between annulus 91 and passageway 25'. Land 92 is of such a length that when control valve spool 49' is moved into its extreme right-hand position, not only is communication between annulus 91 and passageway 25' blocked, but communication between annulus 91 and passageway 37 is also blocked.

The control circuit of FIG. 2 provides four distinct speed ranges for the operation of the self-loading scraper elevator. Any one of these ranges may be selected by the vehicle operator as follows: With elevator control valve 14- in the position as illustrated in FIG. 2, the elevator is in neutral. More specifically, the output of pump 41' flows without obstruction through conduit 42', annulus 47, return passageway 26', and from thence back into reservoir 22 through conduit 29. In a similar manner the output of pump 84 flows without obstruction through conduit 87, branch conduit 89, annulus 91, passageway 37', and back into reservoir 22' through return conduit 29. Since the output fluid from either pump will take the path of least resistance, which is that just described, pressure sufficient to drive the elevator motor 18 is not developed, and the motor is idle.

In order to obtain low speed elevator drive, the operator shifts elevator control valve spool 49' to the right to a low speed position indicated as L. In this position land 52 (exactly as previously described in the case of the circuit of FIG. 1) blocks communication between annulus 47' and return passageway 26'. At the same time, however, land 92 has not yet moved sufficiently to the right to block communication between annulus 91 and return passageway 37. Due to the blockage of communication between annulus 47' and return passageway 26', hydraulic fluid from pump 41' is forced through conduits 81 and 82 into elevator motor 18 thereby driving the elevator mechanism at a low speed. The output of pump 84 having unobstructed passage back to the reservoir, contributes nothing to the operation of elevator motor 18'.

To obtain a medium speed range of the elevator mechanism, the operator further shifts control valve spool 49 completely to the right-hand medium speed position indicated 'by the letter M. In this position land 52 continues to block communication between annulus 47 and return passageway 26. But in addition land 92 now blocks communication between annulus 91 and return passageway 37' whereby output fluid from pump 84 is forced through check valve 38 into conduit 82 and from thence into elevator motor 18'. Thus the outputs of pump 41' and pump 84 are combined to drive elevator motor 18' in the medium speed range.

Two additional elevator speeds are obtainable from the control circuits of FIG. 2. Specifically when control valve spool 49' is in the low speed position L and elevator motor 18' is being driven by the output of pump 41', the operator can actuate foot control lever 66 to move the spool in diverter valve 58' to the extreme left-hand position. This diverts the pressure fluid output from pump 54' away from steering valve 19 into conduit 74' as previously described in connection with FIG. 1. The output of pump 54' is thus combined with the output of pump 41' to drive elevator motor 18 at a higher speed.

Similarly with control valve spool 49' in the extreme right-hand or medium speed M position diverter valve 58' may 'be actuated to divert the output of pump 54 into conduit 74' and from thence into conduit 42. As has been previously described, when in the medium speed M position, the outputs of both pumps 41' and 84 are combined. Diverting the output of pump 54' results in driving elevator motor 18' with the output of the three pumps 41', 84 and 54' respectively. The resultant combined flow of all three pumps through elevator motor 18' produces the highest speed of the elevator mechanism.

The actual speeds obtainable for driving the elevator mechanism are of course dependent upon the relative sizes of pumps 41, 54' and 84. Thus the combinations of the outputs of pumps 41' and 54' may produce an elevator speed greater than the combined outputs of pumps 41' and 84, or vice versa depending upon the relative output capacity of pumps 54 and 84. In any event it will be apparent that suitably selecting the output capacity of any of the aforementioned pumps will enable the vehicle designer to achieve any four combinations of elevator speeds desired.

In both of the previously described control circuits of FIG. 1 and FIG. 2, diversion of the pressure fluid from the steering circuit is accomplished by the manual actuation of the diverter valve. However, it will be noted that the vehicle operator must consciously remove foot pressure from the control lever if he desires to utilize the fast steering capabilities produced by both steering pumps in the steering circuit. In some cases it may be desirable to give priority to the steering system to insure that under conditions Where high speed steering is required the output of both steering pumps is available to the steering valve without relying upon any conscious effort of the vehicle operator. For this purpose a modification of the control circuit as illustrated in FIG. 3 of the drawing, incorporates a pilot operated diverter valve that automatically redirects pressure fluid from the elevator circuit into the steering circuit when high speed steering operation is demanded.

With respect to FIG. 3, parts equivalent to those described in FIG. 1 are given the same indicator numerals with the exception that a double prime is appended thereto. Unless otherwise noted, constructions illustrated in FIG. 3 operate in the same manner as equivalent constmictions illustrated and previously described in FIGS. 1 and 2.

More specifically pump 41 draws hydraulic fluid from reservoir 22" and directs its pressure fluid output to elevator motor 18" through conduits 4-2, 81" and 82". Hydraulic fluid therefrom is also conducted into annulus 47 in elevator control valve 14 through branch conduit 44". Annulus 47 communicates along bore 48" into return passageway 26 and from thence back to reservoir 22" as previously described.

Pump 84" communicates to elevator motor 18" through conduit 87", check valve 88 and conduit 82". The output of pump 84" is further communicated to annulus 91" in elevator control valve 14" by branching conduit 89". Annulus 91 in turn communicates into return passageway 37" along bore 48".

Lands 51" and 92" on elevator valve spool 49" commonly block communication between annulus 47", annulus 91" and passageway 25". At the extreme righthand portion of elevator control valve 14" is an annulus 93 that communicates by means of a passageway and conduit 94 to a pilot piston 96 that bears against one end of a diverter valve spool 97 reciprocally disposed within diverter valve 58". Diverter valve 58 com muni cates at its inlet side with pump 54 while a first outlet communicates via conduit 57" to steering valve 19" (the internal construction of which is shown in US. Patent No. 3,154,921, issued November 3, 1964 to J. A. Junck et al.) and a second outlet therein communicates via conduit 74 with conduit 42". Either the first or second outlets from diverter valve 58" are alternately communicated with the output of pump 54" by suitably positioning diverter valve spool 97.

A pressure feed back conduit 98 communicates conduit 57" to a chamber 99 in diverter valve 58" at the end of diverter valve spool 97 opposite from pilot piston 96.

A pilot passageway 101 in elevator valve spool 49" is of a length sufiicient to communicate annulus 91" with annulus 93 when spool 49" is shifted into the extreme right-hand position.

When elevator valve 14 is in the neutral position the output of pump 41" and pump 84" flow unobstructedly back into reservoir 22 by paths previously described with respect to FIG. 2 whereby elevator motor 18 remains idle. In addition the spring loaded diverter valve spool 97 remains in the extreme leftward position whereby the output of pump 54" is communicated directly to steering valve 19".

To operate the elevator in the low speed range spool 49 is manually shifted to the left into the low L position. In this position land 51" blocks communication between annulus 47 and return passageway 26" whereby the out-put of pump 41" is forced through elevator motor 18". At the same time shifting spool 49" into the low position does not alfect the unobstructed flow of fluid output from pump 84 back to reservoir 22" whereby no fiuid therefrom is contributed to driving elevator pump 18".

To drive the elevator at a medium speed, spool 49" is shifted rightwardly through the neutral position to the medium M speed position. In this position a land 52" blocks communication between annulus 47" and return passageway 26" while land 92 blocks communication between annulus 91" and return passageway 37". Thus the fluid outputs of both pumps 41" and 84" are combined and forced through elevator motor 18" to drive the elevator mechanism at a medium speed.

To drive the elevator mechanism at a high speed, spool 49" is further shifted manually to the extreme right-hand position whereby lands 52" and 92" continue to block the return of pressure fluid directly to reservoir 22", and the outputs of pumps 41" and 84" are combined to drive elevator motor 18". However in addition pressure passageway 101 in spool 49" now communicates annulus 91" into annulus 93 and conduit 94 whereby pressure is exerted upon piiot piston 96 in diverter valve 58".

Pressure on pilot piston 96 in turn forces diverter valve spool 97 into the extreme right-hand position whereby communication between pump 54 and steering valve 19" is interrupted and communication between pump 54" and conduit 74" is opened. Thus the output of pump 54" is combined with the output of pump 41 in conduit 42 and both of these outputs are in turn combined with the output of pump 84 in conduit 82" to drive the elevator motor 18" at a high speed.

In the event high speed steering of the scraper vehicle is demanded at the same time the elevator mechanism is in the high speed range, the output of pump 54 will be automatically redirected into the steering circuit in the following manner:

As the vehicle operator rotates the vehicle steering wheel at a speed sutricient to move the steering valve 19" to a high speed position, pressure in the steering circuit is communicated to conduit 57" through an orifice check valve (constructed according to the orifice check valve shown in US. Patent No. 3,154,921 noted supra) placed internally within steering valve 19", which pressure is in turn communicated into chamber 99 in diverter valve 58" through feed back conduit 98. The build up of pressure in chamber 99 in combination with the spring therein is sufficient to overcome the force of pilot piston 96 against the opposite end of spool 97. Spool 97' then shifts automatically into the extreme left-hand position whereby communication between pump 54 and conduit 74" is interrupted and communication between pump 54" and steering valve 19 is opened. The output of pump 54" is thereby automatically combined in steering valve 19 with the output of steering pump 53" to drive the vehicle steering mechanism at a high speed.

Once high speed steering is no longer demanded, steering valve 19 is shifted such that fluid pressure in conduit 57 is directed back into a reservoir thereby decreasing the pressure whereby pressure within chamber 99 is also decreased. At this time pilot piston 96 once again exerts suflicient pressure to shift diverter valve spool 97 to the extreme right-hand position to once again divert pressure fluid from pump 54" into conduit 74". This fluid is once again combined with the output of pumps 41" and 84" to drive the elevator motor at a high speed.

What is claimed is:

1. In a hydraulic control system including a hydraulically driven motor and at least one other independent hydraulically driven mechanism, the combination comprising: a first source of hydraulic fluid pressure; a second source of hydraulic fluid pressure; and a third source of hydraulic fluid pressure; a first valve means communicating with said first source, a low pressure fluid reservoir and said motor and having a first position in which fluid entering thereinto is directed to the low pressure fluid reservoir and a second position wherein hydraulic fluid entering thereinto is blocked from communication to said reservoir and is thereby forced through said motor; a second valve means communicating with both said second and third sources and controlling said other mechanism; a manually operated diverter valve interposed between said third source and said second valve; said diverter valve having a first normal position in which fluid from said third source is directed to the second valve and a second manually actuated position in which that fluid is diverted from said second valve and is combined with the fluid output from said first source.

2. The hydraulic control system of claim 1 wherein said diverter valve is spring biased into the first nondiverting position.

3. In a hydraulic control system including a hydraulically driven motor and at least one other hydraulically driven mechanism, the combination comprising: a first source of hydraulic fluid pressure; a second source of hydraulic fluid pressure; a third source of hydraulic fluid pressure; and a fourth source of hydraulic fluid pressure; a first valve means communicating with said first and fourth sources and having a first position in which all fluid entering thereinto is directed to a low pressure fluid reservoir, a second position wherein hydraulic fluid from said first source entering thereinto is blocked from said low pressure reservoir and is thereby forced through said motor, a third position wherein hydraulic fluid from both first and fourth sources is blocked from said reservoir; and a connection between said first and fourth sources upstream of the motor whereby fluid from both sources is combined to drive the motor when said first valve is in the third position; a second valve means communicating withboth said second and third sources and controlling said other mechanism; a manually operated diverter valve interposed between said third source and said second valve; said diverter valve having a first normal position in which fluid from said third source is directed to the second valve, and a second manually actuated position wherein that fluid is diverted from said second valve to combine with the fluid output from said first source.

4. The control system of claim 3 wherein hydraulic fluid from said third source is diverted to combine with hydraulic fluid from said fourth source as well as with hydraulic fluid from said first source.

5. The control system of claim 3 wherein the diverter valve is automatically positioned to divert hydraulic fluid away from said second valve in response to fluid pressure developed by said fourth source and is further repositioned to direct hydraulic fluid to said second valve in response to fluid pressure developed by said second source.

6. The control system of claim 5 wherein fluid pressure developed by said fourth source is communicated to said diverter valve when said first valve is in a fourth position; said fluid pressure is exerted upon a pilot piston in said diverter valve to reposition a valve spool therein to divert hydraulic fluid away from the second valve and to combine said fluid with the fluid output of said first source and said fourth source.

7. The control system of claim 6 wherein the second valve has at least one position wherein fluid pressure developed by said second source is applied to the end of the diverter valve opposite from the pilot piston to counteract and overcome the force exerted by said pilot piston to thereby reposition said diverter valve and redirect pressure fluid to said second valve.

8. A hydraulic control system for imparting multiple speeds to the elevator mechanism of a self-loading scraper vehicle comprising: a hydraulic elevator control circuit including at least one source of pressure fluid, elevator control means and an elevator motor; said elevator control means having at least two control positions; one of which directs all hydraulic fluid in the elevator control circuit directly back to a low pressure fluid reservoir, and the other of which directs hydraulic fluid in the elevator control circuit through said motor to drive the elevator mechanism; a hydraulic steering control circuit including at least two independent sources of hydraulic pressure fluid, steering control means, and diverter valve means interposed between said steering control means and one of said sources; said diverter valve means being manually controlled to divert hydraulic pressure fluid away from said steering control means and into said elevator control circuit to combine pressure fluid from the elevator control source and said steering control source to drive the elevator mechanism at a higher speed.

9. The multiple speed elevator control system of claim 3 wherein pressure actuated means are attached to said diverter valve means to automatically divert hydraulic pressure steering fluid into said elevator control circuit and to automatically redivert said pressure fluid back into the steering circuit when demanded by said steering controlmeans.

It). The multiple speed elevator control system of claim 9 wherein said automatic diverter valve means is actuated into the diverting position by a pilot piston driven by pressure from at least one of the elevator circuit pressure fluid sources, and wherein the diverter valve means is actuated into the rediverting position by pressure from the other of said steering pressure fluid sources.

References Cited UNITED STATES PATENTS 2,879,612 3/1959 Schultz et al 6052 XR 3,258,926 7/1966 Iunck et a1 91-411 XR EDGAR W. GEOGHEGAN, Primary Examiner. 

